LinkedIn rolled out Intro about two weeks ago. The idea is relatively simple: make it easier for people to identify who’s emailing them. While the idea is neat, it’s not the cool part. The cool thing about Intro is the implementation: it’s seamlessly integrates with the native iOS Mail app.

See, the LinkedIn team did a great job at correctly identifying who this product is for. It’s certainly not for everybody: lots of people don’t need LinkedIn telling them who their contacts are. That being said, there are lots of Mail powerusers who are productivity junkies: they’re not people who get a handful of emails from grandma every week, they’re the people who get dozens or hundreds of emails every day and respond to them from their phones whenever they get a chance. They’re the people who take advantage of the twenty-second pauses in the day during elevator rides, at stoplights, and while waiting for the train to fire off an email. And they’re the people who don’t have any seconds to spare. This is the demographic Intro is targeting.

For these people, keeping track of who’s who is a very real problem. Keeping the time spent finding out who’s who as short as possible is also a very real problem. That’s why integrating Intro right into the Mail app is so neat—the alternative involves clicking out of the app, opening the LinkedIn app, waiting for a page load, running a search—you get the point. Intro makes a lookup a one-click process.

Intro is also nice because it solve a problem without being at all unwieldy. Once it’s set up, it’s just there: it doesn’t require anything to be turned on or activated in any way, it doesn’t require an app to be opened, it doesn’t need to be called. It simply injects a little banner onto the the top of every email, unobtrusive until it’s clicked. It doesn’t even really need an internet connection to run: because Intro adds HTML and CSS to emails when they’re downloaded from the server, it still works on downloaded messages when you’re no longer in internet range.

The implementation itself is a super clever solution to a tricky problem: how can outside developers extend the functionality of Mail? There are two big constraints here:

• The functionality should happen if the app has been installed on the user’s device regardless of whether the sender has installed it, and
• The functionality can’t in any way modify the way Mail runs.

This doesn’t leave much for developers to work with: if they can’t modify messages when they’re sent, and they can’t change the way messages are received, what can they do?

The Intro team recognized that there is a middleman in the process: the IMAP server.

The team took advantage of this middleman and built their own IMAP server, a proxy which calls on the main server, processes the messages returned by it, and sends them back to the receiving device. In doing this, Intro is able to change the content of an email itself—without ever needing to touch it on either phone.

I think this is pretty exciting stuff. This is partly because it’s a super-lightweight, super-convenient and super-effective solution to a tricky problem, and partly because it’s a new, innovative technique that I don’t think has ever been done before. Injecting content into emails via an intermediate proxy server is a clever workaround that could lead to a whole slew of future applications: translating message contents into another language at the time of download comes to mind, or integrating other social networks or feeds.

Of course, the technique does assume a certain amount of user trust in the provider: it essentially grants the service provider the ability to view and change any email, or track information to be used or sold without the user’s knowledge. LinkedIn claims that their proxy service only processes emails without saving them, but there’s little way for the user to know that first-hand. One solution for this may be to allow users to toggle the functionality for well-known contacts, allowing their messages to skip the proxy and go directly from the IMAP email provider to the receiving device, thus reducing the data that the service provider can collect and protecting sensitive information.

Ultimately, though, I think LinkedIn is onto something with Intro, and I applaud them for their innovation and their product. It’s something I know I’ll use alot, and it has got enough polish to be a pleasure to use. Mostly, though, I’m looking forward to seeing how other companies respond, and I can’t wait to see what kind of other innovations will come of it.